The present invention relates to a cladding resin composition which can be cured by heat, ultraviolet light or an electron beam.
In the conventional resin composition for cladding. purposes, improvement of the electric conductivity of the cured film has been sought by incorporating a conductive substance such as carbon black, and graphite or the like.
However, the practice requires a large quantity of such conductive substance and this causes problems in dispersibility and entails physical degradation of the resin.
It is an object of the present invention to overcome the above-mentioned disadvantages and provide a highly conductive cladding resin composition without involving addition of such conventional conductive substance.
The present invention is, therefore, concerned with a cladding resin composition comprising a polyoxyalkylene polyol phosphate ester (hydroxyl value: 10-2,000 mg KOH/g) and a polymerizable or reactive functional group-containing compound. Reactive functional group-containing compounds include ones that are polymerizable.
The polyoxyalkylene polyol to be used in accordance with the invention can be prepared, for example by addition-polymerizing an alkylene oxide and/or a glycidyl ether with an active hydrogen compound in the presence of a catalyst and removing the catalyst by a per se known purification procedure such as ion exchange, neutralization filtration, adsorption and so on. This polyoxyalkylene polyol preferably has a molecular weight of 200 to 10,000.
The active hydrogen compound mentioned above includes various compounds each having two or more active hydrogen atoms, such as polyhydric alcohols, e.g. ethylene glycol, propylene glycol, 1,4-butanediol, glycerol, trimethylolpropane, sorbitol, sucrose, etc., amine compounds, e.g. monoethanolamine, ethylenediamine, diethylenetriamine, 2-ethylhexylamine, hexamethylenediamine, etc., and phenolic active hydrogen compounds such as bisphenol A, hydroquinone and so on.
The alkylene oxide mentioned above includes, among others, ethylene oxide, propylene oxide, butylene oxide, hexene oxide, cyclohexene oxide, nonene oxide, and xcex1-olefin oxides containing 12 to 28 carbon atoms.
The glycidyl ether mentioned above includes, among others, methyl glycidyl ether, butyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether and so on.
In the addition-pollymerization to the active hydrogen compound, either an alkylene oxide or a glycidyl ether or both may be reacted and, in the latter (copolymerization) case, the order of addition is optional. As the catalyst for this addition-polymerization reaction, a basic catalyst such as sodium methoxide, sodium hydroxide, potassium hydroxide, lithium carbonate, etc. is generally employed but a Lewis acid catalyst such as boron trifluoride or an amine catalyst such as trimethylamine, triethylamine, etc. is also useful. The amount of such catalyst can be the amount generally employed.
The polyoxyalkylene polyol may be partially substituted by a halogen, such as chlorine and/or bromine.
For phosphorylation of such polyoxyalkylene polyol, a phosphorus compound such as diphosphorus pentoxide, phosphoryl trichloride or the like is employed.
The phosphorylation reaction is conducted in the routine manner and the proportions of the polyoxyalkylene polyol and phosphorus compound are such that the product phosphate ester will have a hydroxyl value in the range of 10 to 2,000 mg KOH/g. This phosphate ester may be partially converted to a metal salt, such as an alkali metal salt, e.g. lithium salt, sodium salt or potassium salt. Such a metal salt can be prepared by neutralizing the phosphate ester with an basic alkali metal compound such as lithium hydroxide, sodium hydroxide or potassium hydroxide.
The polymerizable or reactive functional group-containing compound includes, among others, various polyisocyanates, unsaturated compounds such as active hydrogen-containing (meth)acrylates, (meth)acrylic acid, maleic anhydride, etc., glycidyl ether compounds and so on, and these compounds can be used alone or in combination.
Throughout this specification, (meth)acrylic acid means acrylic acid and/or methacrylic acid, while (meth)acrylate represents acrylate and methacrylate.
The polyisocyanate compound includes, among others, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4xe2x80x2-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate etc. as well as mixtures thereof. Polyisocyanates having polyoxyalkylene chains can also be employed.
The polyisocyanate compounds may be used in the form of blocked isocyanates. The blocking agent which can be used for this purpose includes methyl ethyl ketoxime, phenol, caprolactam, ethyl acetoacetate, methanol, sodium hydrosulfite and so on. The blocking can be achieved by adding such a blocking agent to a polyisocyanate and reacting the mixture at 30-90xc2x0 C. for 0.5 to 2 hours.
The active hydrogen-containing (meth)acrylate includes, among others, dihydric alcohol mono(meth)acrylates such as ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate and so on.
The glycidyl ether compound includes, among others, ethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether and sorbitol polyglycidyl ether.
The polyoxyalkylene polyol phosphate ester and the polymerizable or reactive functional group-containing compounds react with each other to give a cured product. When two or more different polymerizable or reactive functional group-containing compounds are employed, all of them may be reacted concurrently or one or more of them be reacted in the first place, with the remainder being reacted thereafter. The proportion of the polymerizable or reactive functional group-containing compound is 1.0 to 10.0 moles per mole of the phosphate ester.
The catalyst for this reaction is selected according to the kind of polymerizable or reactive functional group-containing compound. In the case of polyisocyanates, there may be employed organometal catalysts such as dibutyltin dilaurate, dibutyltin diacetate, phenyl-mercury propionate, lead octenoate, etc. and amine catalysts such as triethylenediamine, N,Nxe2x80x2-dimethyl-piperazine, N-methylmorpholine, tetramethylguanidine, triethylamine, etc. In the case of (meth)acrylic acid, sulfuric acid and p-toluenesulfonic acid may be employed and, where necessary, polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, etc. can be employed in conjunction.
In the cladding resin composition of the invention, said phosphate ester and polymerizable or reactive functional group-containing compound react with each other to give a cured resin. This reaction can be induced by heat, ultraviolet light, an electron beam or the like and, where necessary, a polymerization initiator and a sensitizer may also be used.
Since the cladding resin composition of the invention is highly conductive, it is no longer necessary to incorporate the conventional conductive substance and the composition can be used advantageously in the field of coatings and protective films, etc. where electric conductivity is a requisite.